The invention relates to a mass-balancing device for a reciprocating-piston internal combustion engine. The mass-balancing device comprises a first balancing shaft and a second balancing shaft that is arranged in the first balancing shaft coaxial to this first balancing shaft and that rotates in the opposite sense, wherein the first balancing shaft has at least one bearing point for a first roller bearing and wherein the second balancing shaft has at least one bearing point for a second roller bearing, with the balancing shafts being supported radially in the reciprocating-piston internal combustion engine by these roller bearings.
Such a mass-balancing device emerges from DE 28 22 589 A1, which is considered to be class-forming. The coaxial arrangement of the nested balancing shafts does indeed allow an especially compact construction of the mass-balancing device in the radial direction in comparison with a construction with axis-offset balancing shafts, which is typical in practice, but the technical implementation of the arrangement proposed in the cited publication would have considerable axial structural space requirements. This is based essentially in that all of the roller bearings are allocated to only one or the other balancing shaft and consequently must be arranged one next to the other in the axial direction for corresponding extra requirements for structural space in the axial direction.